Initially, the egg was placed in an incubator before the keeper offered it to the male birds. Once it was inside their nest, the two birds began taking turns sitting on the egg until it hatched, the zoo said.

The parents have begun feeding their adopted young with regurgitated food, the zoo added.

Same-sex behavior has been seen among other birds — scientists say more than 130 bird species are known to engage in homosexual behavior — though a same-sex pair hatching an egg is a first for the Amsterdam zoo.

Reuters Photographer / ReutersThis hours-old baby Griffon vulture was placed in the care of two male foster vultures in 1999.

And back in 1999, two homosexual griffon vultures helped rear two babies at Israel’s Jerusalem zoo, after the chicks were hatched in an incubator.

“They did a great job,” the zoo’s spokeswoman, Sigalit Dvir, said at the time, referring to the first chick. “They shaded him on hot days, they brought him water from a pond, they fed him, they stopped him falling from the nest.”